Authors are being asked to accept a freeze on their library loan income this year, after a letter from culture minister Ed Vaizey confirmed that the rate per library loan would remain unchanged at 6.2 pence for 2013/14.

Writers are remunerated for loans of their work through public libraries under the Public Lending Right (PLR), which will distribute a total pot of £6.1m to authors for 2013/14, a fall of 4.7% from £6.4m in 2012/13.

The rate per loan was maintained at last year's level despite the overall funding decrease due to "super efficiency" of the PLR service, said head of PLR Dr Jim Parker. "We were pleased to be able to keep it at last year's level, as we were worried that it might need to reduce." The administration of PLR was moved to come under the aegis of the British Library in October.

The rate per loan is calculated by dividing the total pot by the number of book loans made through local authority-run public libraries. A total of 1,600 new authors registered to receive PLR this year, up from 1,500 new registrations last year. Two hundred authors qualified for the maximum payout of £6,600 in 2013/14 – for which they need to have notched up 106,000 loans over the year. Last year, 183 authors crossed the 100,000 mark. Authors will receive their PLR statement in January.

Though the rate per loan is to stay the same, the Society of Authors (SoA) wrote to Vaizey outlining its concern over the rise in number of volunteer-run libraries, which are excluded from PLR if they are not affiliated to a local authority.

SoA chief executive Nicola Solomon urged government "to include such [volunteer-run] libraries within the PLR scheme so that a true figure for library lending can be recorded."

However Parker said that the rise of volunteer-run library services had not influenced PLR payments this year. "PLR pays authors for lending through a local authority library. We collect lending data from a sample of libraries, and at the moment there are still enough local authority libraries for us to do that. But given the funding pressure, a lot of community groups are running libraries not contained within a local authority, and they are not covered by PLR." He said that it was a situation "to be watched for the future".

SoA also noted that this year's freeze represented a "15% reduction in funding in real terms over the period 2011/12 to 2014/15, following the 2010 Comprehensive Spending Review".

The total amount paid to authors for library loans has dropped by 19.7% since 2005/06, when the pot was worth £7.6m.

SoA also questioned the slow progress of the extension of PLR to audiobooks and ebooks, which government confirmed in July. A consultation paper was expected before Christmas, but may now not appear until 2014.